Investment casting is one of the oldest known metal-forming processes, dating back thousands of years to when it was first used to produce detailed artwork from metals such as copper, bronze and gold. Industrial investment castings became more common in the 1940's when World War II increased the demand for precisely dimensioned parts formed of specialized metal alloys. Today, investment casting is commonly used in the aerospace and power industries to produce gas turbine components such as airfoils having complex outer surface shapes and internal cooling passage geometries.
The production of a component using the prior art lost wax investment casting process involves producing a ceramic casting vessel including an outer ceramic shell having an inside surface corresponding to the desired outer surface shape of the component, and one or more ceramic cores positioned within the outer ceramic shell corresponding to hollow interior passages to be formed within the component. Molten metal alloy is introduced into the ceramic casting vessel and is then allowed to cool and to solidify. The outer ceramic shell and ceramic core(s) are then removed by mechanical or chemical means to reveal the cast component having the desired external shape and hollow interior volume(s) in the shape of the ceramic core(s).
The known investment casting process is useful for producing components having a limited number of interior passages of relatively simple shape, such as a turbine blade design which includes relatively straight radially extending cooling passages, such as illustrated in U.S. Pat. No. 7,534,089. However, much more complex three dimensional cooling schemes incorporating convoluted 3-D cooling passages will be needed in the near future for advanced gas turbine blades, and the production and use of ceramic cores reflecting such convoluted cooling passages will surpass existing investment casting process capabilities.
Accordingly, an improved method of casting components with interior passageways is needed.